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Tuesday, May 11, 2010

Homework Helper: Hydrogen Fuel for 12 year olds

I'm a bit cynical about Earth Day school projects. Too often it seems like children just "go through the motions" and turn in something because it's required. For example, this year my 12 year old son asked his his little brother what to do for his Earth Day Poster. "It's not for marks, but I have to turn something in tomorrow."

His brother responded by saying, "Oh, that's easy, just draw a big earth, add legs, arms and a mouth, and have him say something like, 'protect the earth, we only have one!'" Working together, they had the job done about 15 minutes. While I appreciated the brotherly love, the obvious lack of real thought tended to confirm my doubts about Earth Day projects.

A few days later, my 12 year old started asking me to explain how hydrogen might be used as a fuel in the future. I put him off (kindly) a few times, before I realized he was really interested. When I asked him how he became curious about hydrogen fuel, he said, "Some kid made an interesting Earth Day poster about how we might be able to use algae to get hydrogen to power all kinds of things." Wow! Maybe those posters are worth doing after all!

OK, so here's my best shot at a seventh standard explanation of the "hydrogen economy" some people like to talk about endlessly. On Thursday, I'll explain how you can use this post to put together a really great summer holiday homework or Earth Day project. (It's up now, here!) (If you are actually in seventh standard and find the reading is difficult, don't be discouraged! The trick to reading hard stuff is to realize nobody understands everything they read--just keep working at it and try to get to the end, where I summarize things simply.) For those who want more details, or want to check my sources, just follow the embedded links.

Hydrogen is the simplest element in the world--no the universe! The sun and stars, for example, are mostly made of hydrogen.

Hydrogen is just one proton and one electron--see the diagram to the right. Hydrogen contains a lot of energy, but it produces almost no pollution when it burns. Liquid hydrogen is so powerful, it can be used to send rockets into space! (The sun, by the way, does not burn hydrogen like this; the sun gets it's power from different process which we call nuclear fusion. This is what powers hydrogen bombs. Unfortunately, we are a long way from figuring how to make nuclear fusion safe and cheap. Nuclear fusion, by the way is not the same as nuclear fission, which powers nuclear power plants and some atomic bombs. )

It's pretty easy to burn hydrogen. When we do that, hydrogen combines with oxygen and gives us heat and water. In addition to burning hydrogen, you can also get energy from it by using something called a fuel cell. In a fuel cell, hydrogen combines with oxygen to produce electricity, heat, clean water, and almost no pollution. Even now, fuel cells can produce useful electricity and power motor vehicles. To create electricity, fuel cells require something called a catalyst, which we'll discuss below in a different context.

So hydrogen is plentiful, clean, and it can power our automobiles and our electrical appliances. What more could we ask for? Unfortunately, there are major problems that need to be solved before we can enter a Utopian "hydrogen economy," where we depend on clean-burning hydrogen instead of fossil fuels. We can group these problems into four categories: Production; Storage and Distribution; and Use. These problems are so major that we need to ask ourselves not just, "Is large scale use of hydrogen possible?" but also, "Is it worth it?" These are important questions to ask whenever we consider technological "fixes." They are especially important when it comes to hydrogen fuel, because converting to a hydrogen economy would be extraordinarily expensive. So it's not something we want to do unless the benefits are very high!

Let's look at each group of problems in turn:

Production
If the world contained massive amounts of cheap hydrogen, we'd already have a hydrogen economy! The problem is that hydrogen is plentiful, but in it's natural state it's almost always combined with other kinds of molecules--water, for example, is just hydrogen and oxygen! Unfortunately, to produce usable hydrogen--to separate the hydrogen from the oxygen in water, for example--you have to use lots of energy. This means we can't really look at hydrogen as an energy source, since you have to use so much energy to get it. Hydrogen is more like a way to store energy, or an energy carrier.

Right now, most hydrogen comes from adding heat to natural gas. This is the cheapest way to get hydrogen. Unfortunately, this process emits lots of greenhouse gases, which cause global warming. You can also get hydrogen by adding electricity to water (electrolysis), which splits the water into hydrogen and oxygen. In addition to electricity, you need something called a catalyst. Catalysts are materials that speed up chemical reactions. Currently, platinum is the catalyst most often used to produce hydrogen gas from water and electricity. That's a problem, because there isn't enough platinum in the world to support a world hydrogen economy--and platinum is expensive even now. The good news is that scientists are developing new, cheaper catalysts.

Assuming we find a cheap enough catalyst, electrolysis would be an environmentally friendly way to produce hydrogen fuel as long as the source of electricity comes from sustainable sources, such as solar or wind power. But we can't even generate enough sustainable electricity to run our light bulbs--we've got a lot of work to do before we'll be able to produce usable hydrogen as well! Increasing our capacity to generate electricity sustainably makes sense, but it's going to take time.

Scientists have found that under certain conditions, algae can produce hydrogen gas. Right now, this process is too expensive to be cost effective, but many hope this will change. Currently, scientists are developing strains of mutant algae that more efficiently use photosynthesis to break down water into oxygen and hydrogen. Sounds a little scary, but who knows? It just might work.

There are other ways of producing hydrogen; these include the next generation nuclear power plants and liquefied coal. These methods have advantages and disadvantages. (Mostly disadvantages, if you ask me, but I won't go into the details of dirty mining and nuclear power here.) Some say we should use coal and natural gas to produce hydrogen until we can figure out more sustainable methods. Or they say we can figure out a way to capture the carbon produced and sequester, or store, it permanently someplace. This is possible, but coal companies will never invest the money it would take to sequester carbon unless they were forced to do so--and governments don't want to do that, because high energy prices are not popular. (For an interesting article on this, read this post and this one at Rapid Uplift. The author is a scientist, so you can quote him!)

Unless we can figure out how to produce hydrogen sustainably, I'm not sure it really makes sense to invest billions of dollars in what it takes to store, distribute, and use hydrogen. Let's look at those problems next.

Storage and Distribution
Hydrogen is tricky stuff to store and transport. But the problems here are not insurmountable, just expensive. Advocates of natural gas use in the US argue that natural gas fueling stations can eventually be converted to hydrogen fueling stations. This does seem to be a strong argument for expansion of Compressed Natural Gas (CNG) infrastructure, since CNG is cheaper and produces fewer emissions than petrol and diesel anyway. But let's not forget that CNG powered automobiles are not sustainable in the long run, because even if they are better than petrol or diesel vehicles, they do produce greenhouse gases. This is especially true if people use cars to to the extent that they do in the US--or New Delhi. To its credit, Delhi has been using CNG to power buses and autorickshaws for years, and it did lead to less pollution--at least until the number of private diesel vehicles drastically increased.

Moving hydrogen from one place to another (distribution) is problematic, because it takes a lot of energy to transport it by truck or train. That leads to inefficiencies--and higher emissions. In the long run, pipelines are the cheapest way to transport hydrogen. The problem is, pipelines are expensive because they need to be specially treated; currently in the US, every 10 km of pipeline costs over six million dollars to build. That's not cheap.

One solution to the transport problem is the produce hydrogen locally--at or near the filling station. So far, most efforts to do this have involved natural gas, which means carbon emissions. If that's the best we can do, it might make sense to drive less and use natural gas directly!

Use
As noted above, there are many ways we can use hydrogen. Fuel cell vehicles, power generation, and rocket ship travel are three! Right now, hydrogen powered cars are very expensive, but those costs will come down with improved technology. Large scale electricity generation from hydrogen probably doesn't make much sense unless we can figure out how to use algae to produce hydrogen cheaply. That may or may not happen. As for rocket ship travel, I wouldn't count on that becoming sustainable in our life time!

Bottom Line:
If we can come up with a cheap, sustainable way to produce hydrogen, it could solve a lot of our current energy problems. I support basic research for this reason. Failing that, it probably makes more sense to keep things simple: use solar and wind power to run light bulbs and to heat water; encourage bicycle use; replace automobiles with trains and natural gas buses; that kind of thing. The good news is that at least some of the infrastructure we use to store and distribute natural gas could eventually be converted for hydrogen use. So if we develop a cheap, sustainable source of hydrogen, the investment we put into fleets of natural gas powered buses won't be a complete waste. Given that, a go-slow approach doesn't close any doors.

What doesn't make sense is to invent a massively expensive infrastructure to make our unsustainable use of automobiles slightly less unsustainable. My advice to seventh standard students? Don't count on hydrogen to solve your future problems, but if you're passionate about science, this is one area where bright minds are required!

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Hari Batti

Hari Batti's Green Light Dhaba

Hari Batti's Green Light Dhaba is based in Delhi and serves up fresh thinking about the environment, politics and justice. We're open Tuesdays, Thursdays and most Saturdays. If we're not pissing somebody off, we're not doing our job. If this is your first visit, check out our brand new About the Dhaba page and tell us what you think; that's why we're here. Of course, if you like what's on the menu, why not grab a free feed or follow us? You can also friend Hari on Facebook, follow him on twitter-- and spread the word in whatever way you can!